Forming self-aligned vias and air-gaps in semiconductor fabrication

ABSTRACT

A semiconductor device includes a first trench on a mandrel line through a top mask layer and stopping at a middle mask layer; and a second trench on a non-mandrel line through the top mask layer and stopping at the middle mask layer. A spacer material is removed from a structure resulting from etching the first trench and the second trench. The device includes a first via structure, formed using a removable material, in the first trench; a second via structure, formed using a removable material, in the second trench; an air-gap formed in a third trench created at a location of the spacer; a fourth trench formed by etching, to remove the first via structure and a first portion of a bottom mask layer under the first via structure; and a self-aligned line-end via on the mandrel line formed by filling the fourth trench with a conductive metal.

TECHNICAL FIELD

The present invention relates generally to a method, system, andcomputer program product for reducing the resistance and/or capacitanceof a current path in vertical fin semiconductor devices. Moreparticularly, the present invention relates to a method, system, andcomputer program product for forming self-aligned vias and air-gaps insemiconductor fabrication.

BACKGROUND

An integrated circuit (IC) is an electronic circuit formed using asemiconductor material, such as Silicon, as a substrate and by addingimpurities to form solid-state semiconductor electronic devices (device,devices), such as transistors, diodes, capacitors, and resistors. Anyreference to a “device” herein refers to a solid-state semiconductorelectronic device unless expressly distinguished where used. Commonlyknown as a “chip” or a “package,” an integrated circuit is generallyencased in hard plastic, forming a “package.” The components in modernday electronics generally appear to be rectangular black plasticpackages with connector pins protruding from the plastic encasement.Often, many such packages are electrically coupled so that the chipstherein form an electronic circuit to perform certain functions.

The software tools used for designing ICs produce, manipulate, orotherwise work with the circuit layout and circuit components on verysmall scales. Some of the components that such a tool may manipulate mayonly measure tens of nanometer across when formed in silicon. Thedesigns produced and manipulated using these software tools are complex,often including hundreds of thousands of such components interconnectedto form an intended electronic circuitry.

A layout includes shapes that the designer selects and positions toachieve a design objective. The objective is to have the shape—thetarget shape—appear on the wafer as designed. However, the shapes maynot appear exactly as designed when manufactured on the wafer throughphotolithography. For example, a rectangular shape with sharp cornersmay appear as a rectangular shape with rounded corners on the wafer.

Once a design layout, also referred to simply as a layout, has beenfinalized for an IC, the design is converted into a set of masks orreticles. A set of masks or reticles is one or more masks or reticles.During manufacture, a semiconductor wafer is exposed to light orradiation through a mask to form microscopic components of the IC. Thisprocess is known as photolithography.

A manufacturing mask is a mask usable for successfully manufacturing orprinting the contents of the mask onto wafer. During thephotolithographic printing process, radiation is focused through themask and at certain desired intensity of the radiation. This intensityof the radiation is commonly referred to as “dose”. The focus and thedosing of the radiation has to be precisely controlled to achieve thedesired shape and electrical characteristics on the wafer. A cut mask isa mask usable to cut or form a pattern in one or more layers ofmaterials during a fabrication process.

A device generally uses several layers of different materials toimplement the device properties and function. A layer of material can beconductive, semi-conductive, insulating, resistive, capacitive, or haveany number of other properties. Different layers of materials have to beformed using different methods, given the nature of the material, theshape, size or placement of the material, other materials adjacent tothe material, and many other considerations.

An IC may use many layers of silicon to implement a circuit. In otherwords, components forming the circuit may be placed on different layersof silicon in a chip. Interconnects connecting the components on onelayer to components on different layers go through the silicon layer.Such interconnects are also known as through silicon vias (TSVs).

The software tools used for designing ICs produce, manipulate, orotherwise work with the circuit layout and circuit components on verysmall scales. Some of the components that such a tool may manipulate mayonly measure a few nanometers across when formed in Silicon. The designsproduced and manipulated using these software tools are complex, oftenincluding hundreds of thousands of such components interconnected toform an intended electronic circuitry.

The illustrative embodiments recognize that the present methods andtechniques for fabricating vias are stretched to their limits due to theincreased complexity of designs, increased density of components,reduced dimensions of the components, and the like. The existing processfor fabricating vias is largely unsuitable for fabricating andinterconnecting inline vias, line-end vias, and air-gaps, that eachalign with the lines in a given IC.

A line is a semiconductor structure formed to carry current to or from asemiconductor device, or in between semiconductor devices. A mandrelline and a non-mandrel line are two different types of lines. An inlinevia is a via that is fabricated on (or aligned with) a mandrel ornon-mandrel line. A line-end via is a via that is fabricated at the endof a mandrel or non-mandrel line.

An air-gap is a hollow space, generally encapsulating vacuum, that iscreated within a structure formed in semiconductor material. An air-gapis used for reducing capacitance between adjacent structures, such asadjacent vias and/or lines. An air-gap can be formed by filling a shapedrecess and pinching the material at the top of the fill.

Inline vias and line-end vias should align with lines, and air-gapsformed between such vias and/or lines should align with the vias and/orlines. Such self-aligned vias and air-gaps are presently difficult tofabricate and interconnect. Therefore, a method for fabricating formingself-aligned vias and air-gaps in semiconductor fabrication would bedesirable.

SUMMARY

The illustrative embodiments provide a method, system, and computerprogram product. An embodiment includes a method that etches a firsttrench at a first location on a mandrel line in a set of mandrel lines,through a top mask layer and stopping at a middle mask layer. Theembodiment etches a second trench at a second location on a non-mandrelline in a set of non-mandrel lines, through the top mask layer andstopping at the middle mask layer. The embodiment removes a spacermaterial from a structure resulting from etching the first trench andthe second trench. The embodiment forms, using a removable material, afirst via structure in the first trench and second via structure in thesecond trench. The embodiment forms an air-gap in a third trench createdat a location of the spacer. The embodiment etches, to remove the firstvia structure and a first portion of a bottom mask layer under the firstvia structure, to form a fourth trench. The embodiment fills the fourthtrench with a conductive metal to form a self-aligned line-end via onthe mandrel line. Thus, the embodiment enables fabricating self-alignedvias on mandrel lines.

Another embodiment further etches, to remove the second via structureand a second portion of the bottom mask layer under the second viastructure, to form a fifth trench. The embodiment fills the fifth trenchwith the conductive metal to form a self-aligned inline via on thenon-mandrel line. Thus, the embodiment enables fabricating self-alignedvias on non-mandrel lines.

In another embodiment, the air-gap is aligned with the first viastructure and the second via structure. Thus, the embodiment enablesfabricating self-aligned air-gaps.

Another embodiment further fills the third trench with a low resistancematerial such that a hollow space is encapsulated within the lowresistance material, the hollow space forming the air-gap. Thus, theembodiment enables fabricating an air-gap.

Another embodiment further stops, as a part of etching the third trench,the third trench at the bottom mask layer. Thus, the embodiment enablesfabricating self-aligned vias and self-aligned air-gaps of one size.

Another embodiment further stops, as a part of etching the third trench,the third trench at the middle mask layer. Thus, the embodiment enablesfabricating self-aligned vias and self-aligned air-gaps of another size.

In another embodiment, the second via structure and a third viastructure are both inline vias, wherein the second via structure isaligned with the third via structure, and wherein the second viastructure and the third via structure are both aligned with thenon-mandrel line. Thus, the embodiment enables fabricating self-alignedvias on mandrel lines and non-mandrel lines, and self-aligned air-gaps.

In another embodiment, the first via structure and a third via structureare both line-end vias, wherein the first via structure is aligned withthe third via structure, and wherein the first via structure and thethird via structure are both aligned with the mandrel line. Thus, theembodiment enables fabricating self-aligned vias on mandrel lines andnon-mandrel lines, and self-aligned air-gaps.

Another embodiment further separates two adjacent vias in the mandrelline with an intervening dielectric structure extending from the middlemask layer to the top mask layer. Thus, the embodiment enablesseparating self-aligned vias.

Another embodiment further fills the first trench and the second trenchwith the removable material up to the top mask layer. Thus, theembodiment enables another method of fabricating self-aligned vias.

Another embodiment further forms, in the structure, above the bottommask layer, the first layer of a first material topped by the middlemask layer. The embodiment forms, above the middle mask layer, thesecond layer of a second material topped by the top mask layer. Thus,the embodiment enables another method of fabricating self-aligned vias.

Another embodiment further removes the top mask layer from above thespacer. The embodiment etches to create the third trench at the locationof the spacer. Thus, the embodiment enables another method offabricating self-aligned vias.

An embodiment includes a computer usable program product. The computerusable program product includes one or more computer-readable storagedevices, and program instructions stored on at least one of the one ormore storage devices.

An embodiment includes a computer system. The computer system includesone or more processors, one or more computer-readable memories, and oneor more computer-readable storage devices, and program instructionsstored on at least one of the one or more storage devices for executionby at least one of the one or more processors via at least one of theone or more memories.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofthe illustrative embodiments when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 depicts a block diagram of a network of data processing systemsin which illustrative embodiments may be implemented;

FIG. 2 depicts a block diagram of a data processing system in whichillustrative embodiments may be implemented;

FIG. 3 depicts a block diagram of a portion of an example process forfabricating example self-aligned inline and line-end vias with air-gapsin accordance with an illustrative embodiment;

FIG. 4 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 5 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 6 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 7 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 8 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 9 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 10 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 11 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 12 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 13 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 14 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment;

FIG. 15 depicts a block diagram of another portion of an example processfor fabricating example self-aligned inline and line-end vias withair-gaps in accordance with an illustrative embodiment; and

FIG. 16 depicts a flowchart of an example process for formingself-aligned vias and air-gaps in semiconductor fabrication inaccordance with an illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments used to describe the invention generallyaddress and solve the above-described problems and other problemsrelated to forming self-aligned vias and air-gaps in semiconductorfabrication.

An embodiment can be implemented as a software application. Theapplication implementing an embodiment can be configured as amodification of an existing semiconductor fabrication system—such as aphotolithography system, as a separate application that operates inconjunction with an existing semiconductor fabrication system, astandalone application, or some combination thereof. For example, theapplication causes the semiconductor fabrication system to perform thesteps described herein, to fabricate a set of inline vias, a set ofline-end vias, and a set of air-gaps, all self-aligned, as describedherein.

For the clarity of the description, and without implying any limitationthereto, the illustrative embodiments are described using certain typesand numerosity of lines, certain types and numerosity of vias, certainnumbers of layers in which to form the vias, certain numbers andpositions of air-gaps. An embodiment can be implemented with a differenttypes and numbers of lines and/or vias, with or without air-gaps, withinthe scope of the illustrative embodiments. An embodiment can beimplemented for fabricating other types of interconnecting structuresthat have to be aligned with certain other structures within the scopeof the illustrative embodiments.

Furthermore, a simplified diagram of the example layout with examplelines and vias is used in the figures and the illustrative embodiments.In an actual fabrication of a circuit, additional structures that arenot shown or described herein, or structures different from those shownand described herein, may be present without departing the scope of theillustrative embodiments. Similarly, within the scope of theillustrative embodiments, a shown or described example structure may befabricated differently to yield a similar operation or result asdescribed herein.

Differently shaded portions in the two-dimensional drawing of thefabricated example structures are intended to represent differentstructures, as described herein. The different structures may befabricated using suitable materials that are known to those of ordinaryskill in the art.

A specific shape or dimension of a shape depicted herein is not intendedto be limiting on the illustrative embodiments. The shapes anddimensions are chosen only for the clarity of the drawings and thedescription and may have been exaggerated, minimized, or otherwisechanged from actual shapes and dimensions that might be used in actuallyfabricating a component or structure according to the illustrativeembodiments.

Furthermore, the illustrative embodiments are described with respect tocertain orientations and directions only as an example. The stepsdescribed by the various illustrative embodiments can be adapted forfabricating other planar and non-planar devices in a similar manner, andsuch adaptations are contemplated within the scope of the illustrativeembodiments. The specific placements of layers, structures, or featuresare also used only as non-limiting examples to describe the variousoperations of the illustrative embodiments. Those of ordinary skill inthe art will be able to use an embodiment to similarly fabricate alignedstructures for other purposes in a similar manner, and such usage isalso contemplated within the scope of the illustrative embodiments.

An embodiment when implemented in an application causes a fabricationprocess to performs certain steps as described herein. The steps of thefabrication process are depicted in the several figures. Not all stepsmay be necessary in a particular fabrication process. Some fabricationprocesses may implement the steps in different order, combine certainsteps, remove or replace certain steps, or perform some combination ofthese and other manipulations of steps, without departing the scope ofthe illustrative embodiments.

A method of an embodiment described herein, when implemented to executeon a device or data processing system, comprises substantial advancementof the functionality of that device or data processing system in formingself-aligned vias and air-gaps in semiconductor fabrication. A manner offabricating line-end vias or other similarly purposed interconnects, isunavailable in the presently available methods. Thus, a substantialadvancement of such devices or data processing systems by executing amethod of an embodiment is in a new ability to fabricate self-alignedinline vias and self-aligned line-end vias with self-aligned air-gaps,or other similarly purposed interconnects.

The illustrative embodiments are described with respect to certain typesof devices, electrical properties, contacts, layers, planes, structures,materials, dimensions, numerosity, data processing systems,environments, components, and applications only as examples. Anyspecific manifestations of these and other similar artifacts are notintended to be limiting to the invention. Any suitable manifestation ofthese and other similar artifacts can be selected within the scope ofthe illustrative embodiments.

Furthermore, the illustrative embodiments may be implemented withrespect to any type of data, data source, or access to a data sourceover a data network. Any type of data storage device may provide thedata to an embodiment of the invention, either locally at a dataprocessing system or over a data network, within the scope of theinvention. Where an embodiment is described using a mobile device, anytype of data storage device suitable for use with the mobile device mayprovide the data to such embodiment, either locally at the mobile deviceor over a data network, within the scope of the illustrativeembodiments.

The illustrative embodiments are described using specific code, designs,architectures, protocols, layouts, schematics, and tools only asexamples and are not limiting to the illustrative embodiments.Furthermore, the illustrative embodiments are described in someinstances using particular software, tools, and data processingenvironments only as an example for the clarity of the description. Theillustrative embodiments may be used in conjunction with othercomparable or similarly purposed structures, systems, applications, orarchitectures. For example, other comparable mobile devices, structures,systems, applications, or architectures therefor, may be used inconjunction with such embodiment of the invention within the scope ofthe invention. An illustrative embodiment may be implemented inhardware, software, or a combination thereof.

The examples in this disclosure are used only for the clarity of thedescription and are not limiting to the illustrative embodiments.Additional data, operations, actions, tasks, activities, andmanipulations will be conceivable from this disclosure and the same arecontemplated within the scope of the illustrative embodiments.

Any advantages listed herein are only examples and are not intended tobe limiting to the illustrative embodiments. Additional or differentadvantages may be realized by specific illustrative embodiments.Furthermore, a particular illustrative embodiment may have some, all, ornone of the advantages listed above.

With reference to the figures and in particular with reference to FIGS.1 and 2, these figures are example diagrams of data processingenvironments in which illustrative embodiments may be implemented. FIGS.1 and 2 are only examples and are not intended to assert or imply anylimitation with regard to the environments in which differentembodiments may be implemented. A particular implementation may makemany modifications to the depicted environments based on the followingdescription.

FIG. 1 depicts a block diagram of a network of data processing systemsin which illustrative embodiments may be implemented. Data processingenvironment 100 is a network of computers in which the illustrativeembodiments may be implemented. Data processing environment 100 includesnetwork 102. Network 102 is the medium used to provide communicationslinks between various devices and computers connected together withindata processing environment 100. Network 102 may include connections,such as wire, wireless communication links, or fiber optic cables.

Clients or servers are only example roles of certain data processingsystems connected to network 102 and are not intended to exclude otherconfigurations or roles for these data processing systems. Server 104and server 106 couple to network 102 along with storage unit 108.Software applications may execute on any computer in data processingenvironment 100. Clients 110, 112, and 114 are also coupled to network102. A data processing system, such as server 104 or 106, or client 110,112, or 114 may contain data and may have software applications orsoftware tools executing thereon.

Only as an example, and without implying any limitation to sucharchitecture, FIG. 1 depicts certain components that are usable in anexample implementation of an embodiment. For example, servers 104 and106, and clients 110, 112, 114, are depicted as servers and clients onlyas example and not to imply a limitation to a client-serverarchitecture. As another example, an embodiment can be distributedacross several data processing systems and a data network as shown,whereas another embodiment can be implemented on a single dataprocessing system within the scope of the illustrative embodiments. Dataprocessing systems 104, 106, 110, 112, and 114 also represent examplenodes in a cluster, partitions, and other configurations suitable forimplementing an embodiment.

Device 132 is an example of a data processing device or a portabledevice usable for computing or communications purposes described herein.For example, device 132 can take the form of a smartphone, a tabletcomputer, a laptop computer, client 110 in a stationary or a portableform, a wearable computing device, or any other suitable device. Anysoftware application described as executing in another data processingsystem in FIG. 1 can be configured to execute in device 132 in a similarmanner. Any data or information stored or produced in another dataprocessing system in FIG. 1 can be configured to be stored or producedin device 132 in a similar manner.

Application 105 implements an embodiment described herein. Fabricationsystem 107 is any suitable system for fabricating a semiconductor deviceor circuit. Application 105 provides instructions to system 107 forfabricating self-aligned inline vias and self-aligned line-end vias withself-aligned air-gaps, or other similarly purposed interconnects, in amanner described herein.

Servers 104 and 106, storage unit 108, and clients 110, 112, and 114 maycouple to network 102 using wired connections, wireless communicationprotocols, or other suitable data connectivity. Clients 110, 112, and114 may be, for example, personal computers or network computers.

In the depicted example, server 104 may provide data, such as bootfiles, operating system images, and applications to clients 110, 112,and 114. Clients 110, 112, and 114 may be clients to server 104 in thisexample. Clients 110, 112, 114, or some combination thereof, may includetheir own data, boot files, operating system images, and applications.Data processing environment 100 may include additional servers, clients,and other devices that are not shown.

In the depicted example, data processing environment 100 may be theInternet. Network 102 may represent a collection of networks andgateways that use the Transmission Control Protocol/Internet Protocol(TCP/IP) and other protocols to communicate with one another. At theheart of the Internet is a backbone of data communication links betweenmajor nodes or host computers, including thousands of commercial,governmental, educational, and other computer systems that route dataand messages. Of course, data processing environment 100 also may beimplemented as a number of different types of networks, such as forexample, an intranet, a local area network (LAN), or a wide area network(WAN). FIG. 1 is intended as an example, and not as an architecturallimitation for the different illustrative embodiments.

Among other uses, data processing environment 100 may be used forimplementing a client-server environment in which the illustrativeembodiments may be implemented. A client-server environment enablessoftware applications and data to be distributed across a network suchthat an application functions by using the interactivity between aclient data processing system and a server data processing system. Dataprocessing environment 100 may also employ a service orientedarchitecture where interoperable software components distributed acrossa network may be packaged together as coherent business applications.

With reference to FIG. 2, this figure depicts a block diagram of a dataprocessing system in which illustrative embodiments may be implemented.Data processing system 200 is an example of a computer, such as servers104 and 106, or clients 110, 112, and 114 in FIG. 1, or another type ofdevice in which computer usable program code or instructionsimplementing the processes may be located for the illustrativeembodiments.

Data processing system 200 is also representative of a data processingsystem or a configuration therein, such as data processing system 132 inFIG. 1 in which computer usable program code or instructionsimplementing the processes of the illustrative embodiments may belocated. Data processing system 200 is described as a computer only asan example, without being limited thereto. Implementations in the formof other data processing devices, such as mobile device 132 in FIG. 1,may modify data processing system 200, such as by adding a touchinterface, and even eliminate certain depicted components from dataprocessing system 200 without departing from the general description ofthe operations and functions of data processing system 200 describedherein.

In the depicted example, data processing system 200 employs a hubarchitecture including North Bridge and memory controller hub (NB/MCH)202 and South Bridge and input/output (I/O) controller hub (SB/ICH) 204.Processing unit 206, main memory 208, and graphics processor 210 arecoupled to North Bridge and memory controller hub (NB/MCH) 202.Processing unit 206 may contain one or more processors and may beimplemented using one or more heterogeneous processor systems.Processing unit 206 may be a multi-core processor. Graphics processor210 may be coupled to NB/MCH 202 through an accelerated graphics port(AGP) in certain implementations.

In the depicted example, local area network (LAN) adapter 212 is coupledto South Bridge and I/O controller hub (SB/ICH) 204. Audio adapter 216,keyboard and mouse adapter 220, modem 222, read only memory (ROM) 224,universal serial bus (USB) and other ports 232, and PCI/PCIe devices 234are coupled to South Bridge and I/O controller hub 204 through bus 238.Hard disk drive (HDD) or solid-state drive (SSD) 226 and CD-ROM 230 arecoupled to South Bridge and I/O controller hub 204 through bus 240.PCI/PCIe devices 234 may include, for example, Ethernet adapters, add-incards, and PC cards for notebook computers. PCI uses a card buscontroller, while PCIe does not. ROM 224 may be, for example, a flashbinary input/output system (BIOS). Hard disk drive 226 and CD-ROM 230may use, for example, an integrated drive electronics (IDE), serialadvanced technology attachment (SATA) interface, or variants such asexternal-SATA (eSATA) and micro-SATA (mSATA). A super I/O (SIO) device236 may be coupled to South Bridge and I/O controller hub (SB/ICH) 204through bus 238.

Memories, such as main memory 208, ROM 224, or flash memory (not shown),are some examples of computer usable storage devices. Hard disk drive orsolid state drive 226, CD-ROM 230, and other similarly usable devicesare some examples of computer usable storage devices including acomputer usable storage medium.

An operating system runs on processing unit 206. The operating systemcoordinates and provides control of various components within dataprocessing system 200 in FIG. 2. The operating system may be acommercially available operating system such as AIX® (AIX is a trademarkof International Business Machines Corporation in the United States andother countries), Microsoft® Windows® (Microsoft and Windows aretrademarks of Microsoft Corporation in the United States and othercountries), Linux® (Linux is a trademark of Linus Torvalds in the UnitedStates and other countries), iOS™ (iOS is a trademark of Cisco Systems,Inc. licensed to Apple Inc. in the United States and in othercountries), or Android™ (Android is a trademark of Google Inc., in theUnited States and in other countries). An object oriented programmingsystem, such as the Java™ programming system, may run in conjunctionwith the operating system and provide calls to the operating system fromJava™ programs or applications executing on data processing system 200(Java and all Java-based trademarks and logos are trademarks orregistered trademarks of Oracle Corporation and/or its affiliates).

Instructions for the operating system, the object-oriented programmingsystem, and applications or programs, such as application 105 in FIG. 1,are located on storage devices, such as in the form of code 226A on harddisk drive 226, and may be loaded into at least one of one or morememories, such as main memory 208, for execution by processing unit 206.The processes of the illustrative embodiments may be performed byprocessing unit 206 using computer implemented instructions, which maybe located in a memory, such as, for example, main memory 208, read onlymemory 224, or in one or more peripheral devices.

Furthermore, in one case, code 226A may be downloaded over network 201Afrom remote system 201B, where similar code 201C is stored on a storagedevice 201D. in another case, code 226A may be downloaded over network201A to remote system 201B, where downloaded code 201C is stored on astorage device 201D.

The hardware in FIGS. 1-2 may vary depending on the implementation.Other internal hardware or peripheral devices, such as flash memory,equivalent non-volatile memory, or optical disk drives and the like, maybe used in addition to or in place of the hardware depicted in FIGS.1-2. In addition, the processes of the illustrative embodiments may beapplied to a multiprocessor data processing system.

In some illustrative examples, data processing system 200 may be apersonal digital assistant (PDA), which is generally configured withflash memory to provide non-volatile memory for storing operating systemfiles and/or user-generated data. A bus system may comprise one or morebuses, such as a system bus, an I/O bus, and a PCI bus. Of course, thebus system may be implemented using any type of communications fabric orarchitecture that provides for a transfer of data between differentcomputer-components or data processing devices attached to the fabric orarchitecture.

A communications unit may include one or more communications-capabledevices used to transmit and receive data, such as a modem or a networkadapter. A memory may be, for example, main memory 208 or a cache, suchas the cache found in North Bridge and memory controller hub 202. Aprocessing unit may include one or more processors or CPUs.

The depicted examples in FIGS. 1-2 and above-described examples are notmeant to imply architectural limitations. For example, data processingsystem 200 also may be a tablet computer, laptop computer, or telephonedevice in addition to taking the form of a mobile or wearable device.

Where a computer or data processing system is described as a virtualmachine, a virtual device, or a virtual component, the virtual machine,virtual device, or the virtual component operates in the manner of dataprocessing system 200 using virtualized manifestation of some or allcomponents depicted in data processing system 200. For example, in avirtual machine, virtual device, or virtual component, processing unit206 is manifested as a virtualized instance of all or some number ofhardware processing units 206 available in a host data processingsystem, main memory 208 is manifested as a virtualized instance of allor some portion of main memory 208 that may be available in the hostdata processing system, and disk 226 is manifested as a virtualizedinstance of all or some portion of disk 226 that may be available in thehost data processing system. The host data processing system in suchcases is represented by data processing system 200.

Four views are shown in each of FIGS. 3-15. each view is of a step of aprocess depicted in each of those figures according to the illustrativeembodiments. Unless otherwise noted for a figure, each of FIGS. 3-15depicts a top view (labelled “TOP”) of the structure in the top leftquadrant of the figure, a sectional view at section AA (labelled “AA”)in the bottom left quadrant of the figure, a sectional view at sectionBB (labelled “BB”) in the bottom right quadrant of the figure, and asectional view at section CC (labelled “CC”) in the top right quadrantof the figure.

With reference to FIG. 3, this figure depicts a block diagram of aportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to produce or manipulate structure 300 asdescribed herein.

Structure 300 is formed on a suitable substrate, in which one or morelayers have been formed. According to the TOP view, structure 300comprises a non-limiting number of non-mandrel lines 302A, 302B, and302C. Similarly, structure 300 comprises a non-limiting number ofmandrel lines 304A and 304B. Structure 300 also comprises a non-limitingnumber of spacer areas 306A, 306B, 306C, and 306D. The non-mandrellines, the mandrel lines, and the spacer areas are intermixed in anon-limiting example manner, as shown.

Sectioning line AA runs through non-mandrel line 302B. The AA view is anelevation view of structure 300 when section 300 is cut at sectioningline AA and a viewer is positioned opposite AA in the direction of thearrows marked on sectioning line AA to observe that elevation.

Sectioning line BB runs through mandrel line 304B. The BB view is anelevation view of structure 300 when section 300 is cut at sectioningline BB and a viewer is positioned opposite BB in the direction of thearrows marked on sectioning line BB to observe that elevation.

Sectioning line CC runs across all mandrel lines, non-mandrel lines, andall spacers. The CC view is a side-elevation view of structure 300 whensection 300 is cut at sectioning line CC and a viewer is positionedopposite CC in the direction of the arrows marked on sectioning line Cto observe that side-elevation.

The AA, BB, and CC views show an example composition of structure 300.For example, according to the AA view, inside or over a suitablesubstrate, metal structures 308 are formed, with example liner 310 of asuitable material. Material 312 is a material suitable for constructingvias and is disposed in the shown example manner relative to structures308-310.

Layer 314 is a hard mask (HM) layer of a suitable material, such as, butnot limited to, a suitable metal. Layer 316 is formed of a materialsuitable for constructing inline vias. Layer 316 is of a depthsufficient to form a portion of a desired height of an inline via, e.g.,20-50 nanometers (nm).

Layer 318 is a trench stop layer of a suitable material that is usablefor stopping a trenching or etching operation that forms a trench orrecess in the material above layer 318. In one example, layer 318 isapproximately 3 nm.

Layer 320 is formed of a material suitable for constructing inline vias.Layer 320 is of a depth sufficient to form another portion of a desiredheight of an inline via, e.g., 50-80 nanometers (nm). The materials ofstructures 312, 316, and 320 may be the same or different from oneanother within the scope of the illustrative embodiments. Layer 322 is ahard mask layer of a suitable material, such as, but not limited to,Tantalum Nitride (TaN). Thus, according to the AA view, layers 308, 310,312, 314, 316, 318, 320, and 322 exist at non-mandrel line, e.g., atnon-mandrel line 302B.

Further according to the BB view, layers 308, 310, and 314 exist at amandrel line, such as at mandrel line 304B, as well. As different fromview AA, view BB shows that layer 326 is created at the location of amandrel line. Layer 326 is formed of a material suitable forconstructing line-end vias. Layer 326 is of a depth sufficient to form aportion of a desired height of a line-end via, e.g., 20-50 nanometers(nm). Layer 318 above layer 326 is the same as in the location of thenon-mandrel line shown in the AA view. Layer 330 is formed of a materialsuitable for constructing line-end vias. Layer 330 is of a depthsufficient to form another portion of a desired height of a line-endvia, e.g., 50-80 nanometers (nm).

The materials of structures 312, 326, and 330 may be the same ordifferent from one another within the scope of the illustrativeembodiments. Furthermore, the materials of structures 316, 320, 326, and330 may be the same or different from one another within the scope ofthe illustrative embodiments. Additionally, the depth of structure 316may be the same or different as the depth of structure 326, and thedepth of structure 320 may be the same or different as the depth ofstructure 330.

In the depicted example, the material for layers 312, 316, 320, 326, and330 are the same, and the demarcation between the mandrel lines and thenon-mandrel lines are not shown in view CC. structures 308 and 310 arethe same as in views AA and BB. Structure 312 is not visible in view CC.Layers 314, 318, and 322 are the same as in views AA and BB. Structures316 and 326 are not perceptibly distinct from one another in thedepicted example owing to the same material in those structures in thenon-limiting example. Structures 320 and 330 are not perceptiblydistinct from one another in the depicted example owing to the samematerial in those structures in the non-limiting example.

Spacers 306A-D are visible above layer 322 in view CC. Non-mandrel lines302A-C are positioned as indicated by arrows in the spaces betweenspacers 306A-D, as shown. Mandrel lines 304A-B are positioned asindicated by arrows in the spaces between spacers 306A-D, as shown.

With reference to FIG. 4, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

An etching operation, such as using a reactive ion etching (REI)process, is performed on structure 300 at non-mandrel lines 302A-C andmandrel lines 304A-B locations. TOP view of this figure shows that anetching operation has been applied at those locations. AA and BB viewsshow that the etching operation has been applied up to trench stop layer318. View CC shows trench 402A, which has been formed at the location ofnon-mandrel line 302A, by etching through HM 322 and removing material320 down to layer 318. Trenches 402B and 402C are formed in a similarmanner. View CC shows trench 404A, which has been formed at the locationof mandrel line 304A, by etching through HM 322 and removing material330 down to layer 318. Trench 404B is formed in a similar manner.

With reference to FIG. 5, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

Views AA and BB do not show any changes at the mandrel and non-mandrelline positions. TOP view and view CC show that the spacer material hasbeen removed to expose HM 322 in the spacer locations 306A-D.

View CC also shows that, as an optional step, a liner of a suitablematerial and thickness can be deposited over HM 322 or as a substitutefor HM 322 (if HM 322 is also removed from the spacer locations by thespacer removal process). Such a deposited liner may be useful to protectthe ultra-low resistance (ULK) material left standing from the trenchingoperation of FIG. 4.

With reference to FIG. 6, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

Remaining trenches 402A-C and 404A-B, as depicted in FIG. 5, are filledwith sacrificial or removable material 502. Some non-limiting examplesof material 502 include, Optical Dispersive Layer (ODL) materials, andChemical-Mechanical Planarization (CMP) material. The TOP and CC viewsshow that the filling of material 502 stops at the level of HM 322.Views AA and BB show material 502 filled above HM 318 up to the top ofHM 322 (not visible in views AA and BB as material 502 obstructs HM 322in those views).

With reference to FIG. 7, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

Self-aligned inline vias are formed in the non-mandrel lines. Forexample, TOP view and view AA show that inline vias 602A, 602B, 602C,and 602D are formed using cut masks, and are aligned with each other andwith non-mandrel line 302B. Similarly, as TOP view shows, inline via602E is a self-aligned with other inline vias in non-mandrel line 302C,and inline via 602F is a self-aligned with other inline vias innon-mandrel line 302A. The inline vias formed in this manner stop at HM322 on the top and HM 314 at the bottom, as shown in view CC. view BBbeing a cut section at a mandrel line has no vias because no vias havebeen formed in any mandrel line.

With reference to FIG. 8, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

Self-aligned line-end vias are formed in the mandrel lines. For example,TOP view and view BB show that line-end vias 702A, 702B, 702C, 702D, and702E are formed using cut masks, and are aligned with each other andwith mandrel line 304B. Depending on their location relative to oneanother, some line-end vias are separated from each other by a suitabledielectric material. For example, line-end vias 702A and 702B areseparated by dielectric 704A; and line-end vias 702C and 702D areseparated by dielectric 704B. The line-end vias and any separatingdielectric structures formed in this manner stop at HM 322 on the topand HM 314 at the bottom, as shown in view CC. View AA cuts through onlynon-mandrel line 302B and therefore only shows inline vias 602A-D. viewCC being a cut section at the location shown, does not cut through anyline-end vias, and therefore does not show any line-end vias formed inany mandrel line.

With reference to FIG. 9, this figure depicts a block diagram of anotherportion of an example process for fabricating example self-alignedinline and line-end vias with air-gaps in accordance with anillustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

The remaining HM 322 after the spacers were removed in FIG. 5, areremoved. The removal of HM 322 reveals or exposes material 320 or 330below, as shown in the TOP view and view CC. views AA and BB do not showthe effect of this removal due to their relative cut locations withrespect to the spacer locations.

With reference to FIG. 10, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

All material located in the spacer locations 306A-D is removed, e.g., byusing RIE. In one embodiment, the removal is performed up to bottom HMlayer 314. The removal creates trenches 1002A, 1002B, 1002C, and 1002Din spacer locations 306A, 306B, 306C, and 306D, respectively, as shownin TOP view and view CC. views AA and BB do not show the effect of thisremoval due to their relative cut locations with respect to the spacerlocations.

With reference to FIG. 11, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

A low resistance (low-K) material is filled in trenches 1002A-D. Low-Kfilling 1102A fills trench 1002A, filling 1102B fills trench 1002B,filling 1102C fills trench 1002D, and filling 1102D fills trench 1002D,as depicted in TOP view and view CC. Furthermore, low-K fillings 1102A-Dare filled in trenches 1002A-D in such a way that air-gaps 1104A, 1104B,1104C, and 1104D are formed in fillings 1102A-D, respectively, asdepicted in TOP view and view CC. For example, low-K material such asSiOCN, SiBCN, SiCNH, or SiC, is filled in a trench and pinched off atthe top to form an air-gap between mandrel line structures and anon-mandrel line structures. views AA and BB do not show the effect ofthis removal due to their relative cut locations with respect to thespacer locations.

With reference to FIG. 11, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

All material located in the spacer locations 306A-D is removed, e.g., byusing RIE. In one embodiment, the removal is performed up to bottom HMlayer 314. The removal creates trenches 1002A, 1002B, 1002C, and 1002Din spacer locations 306A, 306B, 306C, and 306D, respectively, as shownin TOP view and view CC. views AA and BB do not show the effect of thisremoval due to their relative cut locations with respect to the spacerlocations.

With reference to FIG. 12, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

All removable material located in the non-mandrel line locations 302A-Cand mandrel line locations 304A-B is removed, e.g., by using RIE. In oneembodiment, the removal is performed up to a HM layer. For example, asview CC shows, the removal reaches HM layer 314 in non-mandrel linelocations 302A-C, forming trenches 1202A, 1202B, and 1202C,respectively; and the removal reaches HM layer 318 in mandrel linelocations 304A-B, forming trenches 1204A and 1204B, respectively.

TOP view show and view AA show the removal at the via locations in thenon-mandrel layers. Particularly, the removal also removes HM 314 at theinline via locations 1202B, 1202D, 1202E, and 1202F.

TOP view show and view BB show the removal at the via locations in themandrel layers. Particularly, the removal removes HM 314 at the line-endvia locations 1206A, 1206C, 1206D, 1206E, 1206G, and 1206H. The removalleaves the dielectric material at locations 1206C and 1206F undisturbed.

With reference to FIG. 13, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

All trenches formed in FIG. 12 are filled with a suitable metal to formself-aligned inline vias and line-end vias together with self-alignedair-gaps. In one embodiment, a suitable metal liner, such as TitaniumNitride (TiN), is deposited in the trenches before a suitable metal,such as Copper (Cu), is filled in the trenches. This figure depictstrenches 1202A-F, 1204A-B, 1206A-B, 1206D-E, and 1206G-H lines with aliner and filled with a metal in this manner.

With reference to FIG. 14, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

In another embodiment, in a manner similar to the operation described inFIG. 10, all material located in the spacer locations 306A-D is removed,e.g., by using RIE. However, in this embodiment, the removal from thespacer locations is performed only up to middle HM layer 318. Theremoval creates trenches 1402A, 1402B, 1402C, and 1402D in spacerlocations 306A, 306B, 306C, and 306D, respectively, as shown in TOP viewand view CC. views AA and BB do not show the effect of this removal dueto their relative cut locations with respect to the spacer locations.

With reference to FIG. 15, this figure depicts a block diagram ofanother portion of an example process for fabricating exampleself-aligned inline and line-end vias with air-gaps in accordance withan illustrative embodiment. Application 105 in FIG. 1 interacts withfabrication system 107 to further manipulate structure 300 as describedherein.

Further in the embodiment of FIG. 14, in the manner of the etching andair-gap creation operation of FIG. 12, airgaps are created in trenches1402A-D by filling a low-K material 1404A, 1404B, 1404C, and 1404D, andforming air-gaps 1406A, 1406B, 1046C, 1406D, in trenches 1402A-D,respectively, as shown.

Further in this embodiment, trenches are formed in the manner of FIG.13, all trenches formed by the etching similar to the etching of FIG. 12are filled with a suitable metal to form self-aligned inline vias andline-end vias together with self-aligned air-gaps. In one embodiment, asuitable metal liner 1410, such as TiN, is deposited in the trenchesbefore a suitable metal 1408, such as Cu, is filled in the trenches.

With reference to FIG. 16, this figure depicts a flowchart of an exampleprocess for forming self-aligned vias and air-gaps in semiconductorfabrication in accordance with an illustrative embodiment. Process 1600can be implemented in application 105 in FIG. 1.

The application prepares a substrate with at least one layer of materialsuitable for fabricating vias, the layer being topped with a hard masklayer, a trench etch stop layer (middle HM), and a bottom metal cap orhard mask (bottom HM) (block 1602). The application fabricates orlocates mandrel lines and non-mandrel lines with intervening spacers,where the spacers are filled with spacer material above the top HM(block 1604).

The application removes or etches the via material at mandrel andnon-mandrel line sites, etching through the top HM and stopping at themiddle HM, the etching forming vertical structures and trenches (block1606). The application removes the spacer material from above the top HMof the vertical spacer structures that result from the etching of block1606 (block 1608). Optionally, the application deposits additional linermaterial on top of the vertical structures (block 1610).

The application fills the etched trenches from block 1606 with removablematerial up to the top HM (block 1612). The application formsself-aligned vias in the non-mandrel lines (inline vias), starting atthe bottom HM and stopping at the top HM (block 1614). The applicationforms self-aligned vias in the mandrel lines (line-end vias) separatedby a dielectric material, the line-end vias starting at the middle HMand stopping at the top HM (block 1616).

The application removes the top HM from the spacer areas (block 1618).The application trenches the spacer areas up to a suitable HM layer(block 1620). In one case, the trenches extend up to but not through thebottom HM. In another case, the trenches extend to but not through themiddle HM.

The application fills the spacer trenches with low-K insulator such thatthe filling includes an enclosed hollow space (air-gap) within eachspacer trench (block 1622). The application removes the removablematerial that is remaining above the bottom HM and the middle HM layers,including the HM layer material thereunder (block 1624).

The application fills the space vacated by the removed removablematerial and the HM material with a suitable metal and optionally asuitable liner (block 1626). The application ends process 1600thereafter.

Thus, a computer implemented method, system or apparatus, and computerprogram product are provided in the illustrative embodiments for formingself-aligned vias and air-gaps in semiconductor fabrication and otherrelated features, functions, or operations. Where an embodiment or aportion thereof is described with respect to a type of mobile device,the computer implemented method, system or apparatus, the computerprogram product, or a portion thereof, are adapted or configured for usewith a suitable and comparable manifestation of that type of mobiledevice.

Where an embodiment is described as implemented in an application, thedelivery of the application in a Software as a Service (SaaS) model iscontemplated within the scope of the illustrative embodiments. In a SaaSmodel, the capability of the application implementing an embodiment isprovided to a user by executing the application in a cloudinfrastructure. The user can access the application using a variety ofclient devices through a thin client interface such as a web browser(e.g., web-based e-mail), or other light-weight client-applications. Theuser does not manage or control the underlying cloud infrastructureincluding the network, servers, operating systems, or the storage of thecloud infrastructure. In some cases, the user may not even manage orcontrol the capabilities of the SaaS application. In some other cases,the SaaS implementation of the application may permit a possibleexception of limited user-specific application configuration settings.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

What is claimed is:
 1. A method comprising: etching a first trench at afirst location on a mandrel line, through a top mask layer and stoppingat a middle mask layer; removing a spacer material from a structureresulting from etching the first trench and a second trench on anon-mandrel line; forming, using a removable material, a first viastructure in the first trench and second via structure in the secondtrench; forming an air-gap in a third trench created at a location of aspacer; etching, to remove the first via structure and a first portionof a bottom mask layer under the first via structure, to form a fourthtrench; and filling the fourth trench with a conductive metal to form aself-aligned line-end via on the mandrel line.
 2. The method of claim 1,wherein the second trench is etched at a second location on thenon-mandrel line, through the top mask layer and stopping at the middlemask layer, the method further comprising: etching, to remove the secondvia structure and a second portion of the bottom mask layer under thesecond via structure, to form a fifth trench; and filling the fifthtrench with the conductive metal to form a self-aligned inline via onthe non-mandrel line.
 3. The method of claim 1, wherein the air-gap isaligned with the first via structure and the second via structure. 4.The method of claim 1, further comprising: filling the third trench witha low resistance material such that a hollow space is encapsulatedwithin the low resistance material, the hollow space forming theair-gap.
 5. The method of claim 1, further comprising: stopping, as apart of etching the third trench, the third trench at the bottom masklayer.
 6. The method of claim 1, further comprising: stopping, as a partof etching the third trench, the third trench at the middle mask layer.7. The method of claim 1, wherein the second via structure and a thirdvia structure are both inline vias, wherein the second via structure isaligned with the third via structure, and wherein the second viastructure and the third via structure are both aligned with thenon-mandrel line.
 8. The method of claim 1, wherein the first viastructure and a third via structure are both line-end vias, wherein thefirst via structure is aligned with the third via structure, and whereinthe first via structure and the third via structure are both alignedwith the mandrel line.
 9. The method of claim 1, further comprising:separating two adjacent vias in the mandrel line with an interveningdielectric structure extending from the middle mask layer to the topmask layer.
 10. The method of claim 1, further comprising: filling thefirst trench and the second trench with the removable material up to thetop mask layer.
 11. The method of claim 1, further comprising: forming,in the structure, above the bottom mask layer, a first layer of a firstmaterial topped by the middle mask layer; and forming, above the middlemask layer, a second layer of a second material topped by the top masklayer.
 12. The method of claim 1, further comprising: removing the topmask layer from above the spacer; and etching to create the third trenchat the location of the spacer.
 13. The method of claim 1, furthercomprising: locating, in a structure, a set of mandrel lines whichincludes the mandrel line, a set of non-mandrel lines which includes thenon-mandrel line, and a set of spacers, the structure comprising thebottom mask layer, a first layer, the middle mask layer, a second layer,and the top mask layer, and wherein a spacer in the set of spacerscomprises a structure formed above the top mask layer.
 14. A computerusable program product comprising a computer readable storage medium,and program instructions stored on the computer readable storage medium,the program instructions comprising: program instructions to etch afirst trench at a first location on a mandrel line, through a top masklayer and stopping at a middle mask layer; program instructions toremove a spacer material from a structure resulting from etching thefirst trench and a second trench on a non-mandrel line; programinstructions to form, using a removable material, a first via structurein the first trench and second via structure in the second trench;program instructions to form an air-gap in a third trench created at alocation of a spacer; program instructions to etch, to remove the firstvia structure and a first portion of a bottom mask layer under the firstvia structure, to form a fourth trench; and program instructions to fillthe fourth trench with a conductive metal to form a self-alignedline-end via on the mandrel line.
 15. A semiconductor device comprising:a first trench etched at a first location on a mandrel line, through atop mask layer and stopping at a middle mask layer, wherein a spacermaterial is removed from a structure resulting from etching the firsttrench and a second trench on a non-mandrel line; a first via structure,formed using a removable material, in the first trench; a second viastructure, formed using the removable material, in the second trench; anair-gap formed in a third trench created at a location of a spacer; afourth trench formed by etching, to remove the first via structure and afirst portion of a bottom mask layer under the first via structure; anda self-aligned line-end via on the mandrel line formed by filling thefourth trench with a conductive metal.
 16. The semiconductor device ofclaim 15, wherein the second trench is etched at a second location onthe non-mandrel line, through the top mask layer and stopping at themiddle mask layer, the semiconductor device further comprising: a fifthtrench formed by etching, to remove the second via structure and asecond portion of the bottom mask layer under the second via structure;and a self-aligned inline via on the non-mandrel line formed by fillingthe fifth trench with the conductive metal.
 17. The semiconductor deviceof claim 15, wherein the air-gap is aligned with the first via structureand the second via structure.
 18. The semiconductor device of claim 15,further comprising: a low resistance material filling the third trenchsuch that a hollow space is encapsulated within the low resistancematerial, the hollow space forming the air-gap.
 19. The semiconductordevice of claim 15, wherein as a part of etching the third trench, thethird trench is stopped at the bottom mask layer.
 20. The semiconductordevice of claim 15, wherein as a part of etching the third trench, thethird trench is stopped at the middle mask layer.